The diagnosis of renal agenesis is often difficult. Four cases are presented, two of which are proved cases of unilateral agenesis and appear to sattsfy the criteria for the condition, one is a probable renal agenesis, and the last a small, fibrosed, functionless kidney, of tuberculous disease.

The three agenetic cases all presented with pain or discomfort on the affected side, i.e., the left side, the reason for this being obscure. They amply illustrate the appearances found at various stages of investigation, and the diffiqulties experienced in interpreting the results and findings. There appears to be a definite preponderance of renal agenesis on the left side.

I wish to thank Mr W. S. Mack for affording me the opportunity of presenting these cases, and for his invaluable criticisms and suggestions in the preparation of the article; and Mr Gabriel Donald for the excellent illustrations.